In the data communication field, with the rise of the network protocol television (IPTV), the video conference, and the network radio station, more and more manufacturers and services begin to support an application of multicast message. The multicast is to realize the data transmission mode from a simple point to multiple points in the network, which can save the network bandwidth, reduce the network load, and improve the transmission efficiency of the network.
In the current exchange system of the router and the switchboard, the replication of the multicast message is achieved by the uplink side and downlink side together. At the uplink side, the replication among different line cards is realized by the exchange network, and the amount of replication is limited; while at the downlink side, it is to replicate within the line card, which needs to perform the replication with large data volume. When the multicast replication is performed in the downlink side line card, if the messages queue up in the output port directly after the replication is finished by adopting the traditional mode, it will consume a large amount of memory resources, and is unfavorable to perform the replication with large data volume. Meanwhile its structure is unfavorable to the expansion of the number of ports as well, and the replication among the ports will interfere with each other as well.